#!/usr/bin/env python
################################################################################
#
#   indirect_iter.py
# 
# 
#       iterate the items which match an index
#
#
#   Copyright (C) 2007 Leo Goodstadt
#
#   This program is free software; you can redistribute it and/or
#   modify it under the terms of the GNU General Public License
#   as published by the Free Software Foundation; version 2
#   of the License
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program; if not, write to the Free Software
#   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
#################################################################################


from itertools import izip

def indirect_iter (sequence, index_iter):
    """
    returns values at the specified indices
    N.B. Out of order indices are ignored
    """
    index_iter = iter(index_iter)
    try:
        next_index = index_iter.next()
        for i, v in enumerate(iter(sequence)):
            if i == next_index:
                yield v
                while next_index <= i:
                    next_index = index_iter.next()
    except StopIteration:
        return
    
    
def unit_test():
    values = list("asdfasbbasgasggsadf")
    for i in indirect_iter(values,  [0, 3, 13, 11, 5, 17]):
        print i
        
if __name__ == '__main__':
    unit_test()




